//
//  UIImage+Blur.m
//  Popping
//
//  Created by André Schneider on 10.07.14.
//  Copyright (c) 2014 André Schneider. All rights reserved.
//

#import "UIImage+Blur.h"
#import <Accelerate/Accelerate.h>

@implementation UIImage (BlurGlass)

- (UIImage*)blur
{
    return [self imgWithLightAlpha:0.1 radius:3 colorSaturationFactor:1];
}

- (UIImage*)imgWithLightAlpha:(CGFloat)alpha radius:(CGFloat)radius colorSaturationFactor:(CGFloat)colorSaturationFactor
{
    UIColor* tintColor = [UIColor colorWithWhite:1.0 alpha:alpha];
    return [self imgBluredWithRadius:radius tintColor:tintColor saturationDeltaFactor:colorSaturationFactor maskImage:nil];
}

- (UIImage*)imgBluredWithRadius:(CGFloat)blurRadius tintColor:(UIColor*)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage*)maskImage
{

    CGRect imageRect = { CGPointZero, self.size };
    UIImage* effectImage = self;

    BOOL hasBlur = blurRadius > __FLT_EPSILON__;
    BOOL hasSaturationChange = fabs(saturationDeltaFactor - 1.) > __FLT_EPSILON__;
    if (hasBlur || hasSaturationChange) {
        UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]);
        CGContextRef effectInContext = UIGraphicsGetCurrentContext();
        CGContextScaleCTM(effectInContext, 1.0, -1.0);
        CGContextTranslateCTM(effectInContext, 0, -self.size.height);
        CGContextDrawImage(effectInContext, imageRect, self.CGImage);

        vImage_Buffer effectInBuffer;
        effectInBuffer.data = CGBitmapContextGetData(effectInContext);
        effectInBuffer.width = CGBitmapContextGetWidth(effectInContext);
        effectInBuffer.height = CGBitmapContextGetHeight(effectInContext);
        effectInBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectInContext);

        UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]);
        CGContextRef effectOutContext = UIGraphicsGetCurrentContext();
        vImage_Buffer effectOutBuffer;
        effectOutBuffer.data = CGBitmapContextGetData(effectOutContext);
        effectOutBuffer.width = CGBitmapContextGetWidth(effectOutContext);
        effectOutBuffer.height = CGBitmapContextGetHeight(effectOutContext);
        effectOutBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectOutContext);

        if (hasBlur) {
            CGFloat inputRadius = blurRadius * [[UIScreen mainScreen] scale];
            int radius = floor(inputRadius * 3. * sqrt(2 * M_PI) / 4 + 0.5);
            if (radius % 2 != 1) {
                radius += 1; // force radius to be odd so that the three box-blur methodology works.
            }
            vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend);
            vImageBoxConvolve_ARGB8888(&effectOutBuffer, &effectInBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend);
            vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend);
        }
        BOOL effectImageBuffersAreSwapped = NO;
        if (hasSaturationChange) {
            CGFloat s = saturationDeltaFactor;
            CGFloat floatingPointSaturationMatrix[] = {
                0.0722 + 0.9278 * s, 0.0722 - 0.0722 * s, 0.0722 - 0.0722 * s, 0,
                0.7152 - 0.7152 * s, 0.7152 + 0.2848 * s, 0.7152 - 0.7152 * s, 0,
                0.2126 - 0.2126 * s, 0.2126 - 0.2126 * s, 0.2126 + 0.7873 * s, 0,
                0, 0, 0, 1,
            };
            const int32_t divisor = 256;
            NSUInteger matrixSize = sizeof(floatingPointSaturationMatrix) / sizeof(floatingPointSaturationMatrix[0]);
            int16_t saturationMatrix[matrixSize];
            for (NSUInteger i = 0; i < matrixSize; ++i) {
                saturationMatrix[i] = (int16_t)roundf(floatingPointSaturationMatrix[i] * divisor);
            }
            if (hasBlur) {
                vImageMatrixMultiply_ARGB8888(&effectOutBuffer, &effectInBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags);
                effectImageBuffersAreSwapped = YES;
            }
            else {
                vImageMatrixMultiply_ARGB8888(&effectInBuffer, &effectOutBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags);
            }
        }
        if (!effectImageBuffersAreSwapped)
            effectImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

        if (effectImageBuffersAreSwapped)
            effectImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }

    // 开启上下文 用于输出图像
    UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]);
    CGContextRef outputContext = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(outputContext, 1.0, -1.0);
    CGContextTranslateCTM(outputContext, 0, -self.size.height);

    // 开始画底图
    CGContextDrawImage(outputContext, imageRect, self.CGImage);

    // 开始画模糊效果
    if (hasBlur) {
        CGContextSaveGState(outputContext);
        if (maskImage) {
            CGContextClipToMask(outputContext, imageRect, maskImage.CGImage);
        }
        CGContextDrawImage(outputContext, imageRect, effectImage.CGImage);
        CGContextRestoreGState(outputContext);
    }

    // 添加颜色渲染
    if (tintColor) {
        CGContextSaveGState(outputContext);
        CGContextSetFillColorWithColor(outputContext, tintColor.CGColor);
        CGContextFillRect(outputContext, imageRect);
        CGContextRestoreGState(outputContext);
    }

    // 输出成品,并关闭上下文
    UIImage* outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return outputImage;
}

@end